Just having a look through my current save (Year 2020 - Manager of Oldham) none of the 'European Giants' have been relegated but the odd team here and there are no longer a major force.
Liverpool are beginning to struggle over the last few seasons.
2016/17 - 12th
2017/18 - 14th
2018/19 - 14th
2019/20 - 16th
The other "big teams" in the Premier League have all being taking up the top six places in the Premier League.
No major falls from grace, the only real surprise you could say was that it took PSG until 2019 to finally lift the French League title.
Again no real surprises in this league, Werder and Dortmund have had the odd bad season here and there but nothing major as in the other seasons they have been in the CL places or chasing for the title.
Feyenoord had a terrible season in 2014/15 where they finished second bottom (17th) but managed to avoid relegation by winning their Relegation Play-Off games. Ever since that season they have been always finished in the mid table or bottom half of the League.
AC Milan have gone from title challengers to an average mid table side, in 2014/15 they had their lowest ever league finish where they finished the League in 15th. However the season after they finished 4th but have struggled since with finishes in 12th, 11th & 14th.
Juventus had one dreadful season in 2019/20 ending up 16th - which was very bizarre since they won Serie A the season before!!
Malaga were relegated finishing 18th in 2014/15, but bounced straight back to La Liga. Suppose you could count Barcelona not finishing in the top three for the last three seasons as a surpise, although the lowest finish was only 5th.
While overall no big teams have fallen really, some other teams have become title challengers, the most noteable is Genoa who have become one of the top sides in Italy (without a Tycoon takeover) consistently challenging for the Serie A title - despite winning it it only once they haven't finished outside the top three in any of the last five seasons. On the International Stage all the major Nations still compete for the Euro's and World Cup with the odd team having a bad tournament here and there. The main surprise was Belgium winning the 2016 Euro's and Mexico winning the 2018 World Cup.